KR20230003642A - Method and device for applying dynamic range compression to a higher order ambisonics signal - Google Patents

Abstract

Dynamic Range Control (DRC) simply cannot be applied to Higher Order Ambisonics (HOA) based signals. A method of performing DRC on an HOA signal includes transforming the HOA signal into the spatial domain, analyzing the transformed HOA signal, and obtaining gain factors usable for dynamic compression from the results of the analyzing step. Include steps. Gain factors may be transmitted along with the HOA signal. When applying DRC, the HOA signal is transformed to the spatial domain, gain factors are extracted and multiplied with the transformed HOA signal in the spatial domain, where a gain compensated transformed HOA signal is obtained. The gain-compensated transformed HOA signal is converted back to the HOA region, where a gain-compensated HOA signal is obtained.

Description

Method and device for applying dynamic range compression to higher order ambisonics signals

The present invention relates to a method and device for performing Dynamic Range Compression (DRC) on an Ambisonics signal, and in particular a Higher Order Ambisonics (HOA) signal.

The purpose of DRC (Dynamic Range Compression) is to reduce the dynamic range of an audio signal. A time-varying gain factor is applied to the audio signal. Typically, this gain factor depends on the amplitude envelope of the signal used to control the gain. Mapping is usually non-linear. Large amplitudes are mapped to smaller amplitudes, while faint sounds are often amplified. Scenarios are noisy environments, late night listening, listening on small speakers or mobile headphones.

A common concept for streaming or broadcasting audio is to generate a DRC gain prior to transmission and apply this gain after receiving and decoding. The principle of using DRC - ie how DRC is normally applied to audio signals - is shown in Fig. 1 a). The signal level, which is usually the signal envelope, is detected and the associated time-varying gain (g _DRC ) is calculated. Gain is used to change the amplitude of an audio signal. Fig. 1b) shows the principle of using DRC for encoding/decoding, where gain factors are transmitted together with the coded audio signal. At the decoder side, a gain is applied to the decoded audio signal to reduce the dynamic range of the decoded audio signal.

For 3D audio, different gains may be applied to speaker channels representing different spatial locations. These locations then need to be known at the transmit side in order to be able to generate a matching gain set. While this is usually only possible for idealized conditions, in real life the number of speakers and their placement varies in many ways. This is influenced more by practical considerations than by specifications. HOA (Higher Order Ambisonics) is an audio format that enables flexible rendering. The HOA signal consists of coefficient channels that do not directly represent sound levels. Therefore, DRC cannot simply be applied to HOA-based signals.

The present invention at least solves the problem of how DRC can be applied to HOA signals. The HOA signal is analyzed to obtain one or more gain factors. In one embodiment, at least two gain factors are obtained, and analysis of the HOA signal includes transformation to the spatial domain (iDSHT). One or more gain factors are transmitted along with the original HOA signal. A special indication may be sent to indicate whether all gain factors are equal. In so-called simplified mode this is the case, whereas in non-simplified mode at least two different gain factors are used. At the decoder, one or more gains may (but need not be) be applied to the HOA signal. The user can choose whether to apply one or more gains. The advantage of the simplified mode is that it requires significantly less computation, since only one gain factor is used, and since the gain factor can be directly applied to the coefficient channels of the HOA signal in the HOA domain, thus The conversion to the spatial domain and the subsequent conversion to the HOA domain can be omitted. In the simplified mode, the gain factor is obtained by analyzing only the 0th order coefficient channel of the HOA signal.

According to an embodiment of the present invention, a method for performing DRC on an HOA signal includes converting the HOA signal to the spatial domain (by inverse DSHT), analyzing the converted HOA signal, and analyzing the HOA signal. and obtaining usable gain factors for dynamic range compression from the results of the step. In further steps, the obtained gain factors are multiplied (in the spatial domain) with the transformed HOA signal, where a gain compressed transformed HOA signal is obtained. Finally, the gain-compressed transformed HOA signal is converted (by DSHT) back to the HOA domain, that is, the coefficient domain, where the gain-compressed HOA signal is obtained.

Furthermore, according to an embodiment of the present invention, a method for performing DRC on an HOA signal in a simplified mode includes analyzing the HOA signal and a gain factor usable for dynamic range compression from the results of the analyzing step. It includes the step of obtaining. In further steps, upon evaluation of the indication, the obtained gain factor is multiplied (in the HOA domain) with the coefficient channels of the HOA signal, where a gain compressed HOA signal is obtained. Also upon evaluation of the indication, it may be determined that conversion of the HOA signal may be omitted. An indication indicating that the simplified mode - i.e., only one gain factor is used - is either implicitly - eg, where only the simplified mode can be used due to hardware or other limitations - or explicitly - e.g. , upon user selection of either a simplified mode or a non-simplified mode - may be set.

Moreover, according to one embodiment of the present invention, a method of applying DRC gain factors to an HOA signal includes receiving an HOA signal, an indication and gain factors, determining that an indication represents an unsimplified mode, (inverse DSHT transforming the HOA signal to the spatial domain using ), a transformed HOA signal is obtained, multiplying the gain factors with the transformed HOA signal, and a dynamic range compressed transformed HOA signal is obtained. -, and transforming the dynamic range compressed transformed HOA signal (using DSHT) back to the HOA domain (ie coefficient domain) - a dynamic range compressed HOA signal is obtained. Gain factors may be received together with or separately from the HOA signal. Moreover, according to an embodiment of the present invention, a method of applying a DRC gain factor to an HOA signal includes receiving the HOA signal, an indication and a gain factor, determining that the indication represents a simplified mode, and upon determining the indication. , multiplying the gain factor with the HOA signal, whereby a dynamic range compressed HOA signal is obtained. Gain factors may be received together with or separately from the HOA signal.

A device for applying DRC gain factors to an HOA signal is disclosed in claim 11 .

In one embodiment, the present invention provides a computer readable medium having executable instructions that cause a computer to perform a method of applying DRC gain factors to an HOA signal comprising steps as described above.

In one embodiment, the present invention provides a computer readable medium having executable instructions that cause a computer to perform a method of performing DRC on an HOA signal comprising steps as described above.

Advantageous embodiments of the invention are disclosed in the dependent claims, the following description and the drawings.

Exemplary embodiments of the present invention are described with reference to the accompanying drawings.
1 shows the general principle of DRC applied to audio;
Figure 2 shows a general approach for applying DRC to HOA-based signals, in accordance with the present invention;
Figure 3 shows a spherical speaker grid for N=1 to N=6;
Figure 4 shows generating DRC gains for HOA;
5 is a diagram showing applying DRC to an HOA signal;
Fig. 6 shows dynamic range compression processing at the decoder side;
Fig. 7 shows DRC for HOA in QMF domain combined with rendering step;
Fig. 8 shows DRC for HOA in QMF domain combined with a rendering step for the simple case of a single DRC gain group;

The present invention describes how DRC can be applied to HOA. This has not been easy in the past because HOA is a sound field description. Figure 2 shows the principle of the approach. On the encoding side or transmitting side, as shown in a) of Fig. 2, the HOA signals are analyzed, DRC gains g are calculated from the analysis of the HOA signal, the DRC gains are coded and transmitted together with the coded representation of the HOA content. do. This can be a multiplexed bitstream or two or more separate bitstreams.

On the decoding or receiving side, gains g are extracted from this bitstream or bitstreams, as shown in Fig. 2b). After decoding the bitstream or bitstreams at the decoder, gains g are applied to the HOA signal as described below. By this, gains are applied to the HOA signal - that is, in general, a dynamic range reduced HOA signal is obtained. Finally, the dynamic ranged HOA signal is rendered in the HOA renderer.

In the following, the assumptions and definitions used are explained.

The assumptions are that the HOA renderer is energy preserving - that is, N3D normalized spherical harmonics are used, and the energy of the unidirectional signal coded inside the HOA representation is preserved after rendering. How to achieve this energy conserving HOA rendering is described, for example, in WO2015/007889A _(PD130040) .

Definitions of terms used are as follows.

는 τ 개의 HOA 샘플들의 블록인

를 나타내고, 여기서 벡터

는 앰비소닉스 계수들을 ACN 순서로 포함한다(벡터 인덱스 o = n² + n + m + 1이고, 여기서 n은 계수 위수 인덱스(coefficient order index)이고 m은 계수 차수 인덱스(coefficient degree index)임). N은 HOA 절단 차수(HOA truncation order)를 나타낸다. b에서의 고차 계수들의 개수는 (N + 1)²이다. 하나의 데이터 블록에 대한 샘플 인덱스는 t이다. τ는 보통 하나의 샘플부터 64 개의 샘플 또는 그 이상까지의 범위에 있을 수 있다.

is a block of τ HOA samples

, where vector

contains Ambisonics coefficients in ACN order (vector index o = n ² + n + m + 1, where n is the coefficient order index and m is the coefficient degree index). N represents the HOA truncation order. The number of higher order coefficients in b is (N + 1) ² . The sample index for one data block is t. τ can usually range from 1 sample to 64 samples or more.

는 B의 첫 번째 행이다.0th order signal

is the first row of B.

는 공간 영역에서 HOA 샘플들의 블록을 L 개의 스피커 채널의 블록으로 렌더링하는 에너지 보존 렌더링 행렬을 나타내고: W = DB이고, 여기서

이다. 이것은 도 2의 b)에서의 HOA 렌더러의 가정된 절차(HOA 렌더링)이다.

denotes an energy conservation rendering matrix rendering a block of HOA samples into a block of L speaker channels in the spatial domain: W = DB , where

to be. This is the assumed procedure of the HOA renderer (HOA rendering) in Fig. 2b).

는 구면 상에 아주 규칙적인 방식으로 - 모든 이웃하는 위치들이 동일한 거리를 공유하는 방식으로 - 배치되는 L_L = (N + 1)² 개의 채널들에 관련된 렌더링 행렬을 나타낸다. D _L은 양호 조건(well-conditioned)이고, 그의 역 D _L ^-1이 존재한다. 이와 같이, 둘 다는 한 쌍의 변환 행렬(DSHT - Discrete Spherical Harmonics Transform)을 정의한다:

denotes the rendering matrix associated with L _L = (N + 1) ² channels that are placed in a very regular way on the sphere - in such a way that all neighboring locations share the same distance. D _L is well-conditioned, and its inverse D _L ^-1 exists. As such, both define a pair of transformation matrices (DSHT - Discrete Spherical Harmonics Transform):

W _L = D _L B , B = D _L ^-1 W _L

g is a vector of L _L = (N + 1) ² gain DRC values. The gain values are assumed to apply to a block of τ samples, and are assumed to be smooth from block to block. For transmission, gain values that share the same values may be combined into gain groups. If only one gain group is used, this means that a single DRC gain value, here denoted by g ₁ , is applied to all speaker channel τ samples.

For every HOA truncation order N, an ideal L _L = (N + 1) ² imaginary speaker grid and associated rendering matrix D _L are defined. Imaginary speaker locations sample areas of space surrounding the imaginary listener. The grids for N=1 to 6 are shown in Figure 3, where the areas related to the speaker are shaded cells. One sampling location is always relative to the center speaker location (azimuth = 0, inclination = π/2; note that azimuth is measured from the frontal direction relative to the listening position). When DRC gains are generated, the encoder side knows the sampling positions D _L and D _L ^-1 . At the decoder side, it is necessary to know D _L and D _L ^-1 to apply the gain values.

Generation of DRC gains for HOA is done as follows.

이 이 신호들을 분석하는 것에 의해 생성된다. 콘텐츠가 HOA와 AO(Audio Object: 오디오 객체)의 조합이면, 예컨대, 대화 트랙과 같은 AO 신호들이 사이드 체이닝(side chaining)을 위해 사용될 수 있다. 이것이 도 4의 b)에 도시되어 있다. 상이한 공간 영역들에 관련된 상이한 DRC 이득 값들을 생성할 때, 이 이득들이 디코더측에서의 공간 이미지 안정성(spatial image stability)에 영향을 주지 않도록 주의를 기울일 필요가 있다. 이것을 피하기 위해, 가장 간단한 경우(소위 단순화된 모드)에, 단일의 이득이 L 개의 채널들 모두에 할당될 수 있다. 이것은 모든 공간 신호들 W를 분석하는 것에 의해 또는 0차 HOA 계수 샘플 블록

을 분석하는 것에 의해 행해질 수 있고, 공간 영역으로의 변환이 필요하지 않다(도 4의 a)). 후자는 W의 다운믹스 신호(downmix signal)를 분석하는 것과 동일하다. 추가 상세가 이하에서 주어진다.The HOA signal is converted to the spatial domain by W _L = D _L B . Max L _L = (N + 1) ² DRC gains

is created by analyzing these signals. If the content is a combination of HOA and AO (Audio Object), AO signals such as, for example, a dialogue track may be used for side chaining. This is shown in Figure 4b). When generating different DRC gain values related to different spatial regions, care needs to be taken that these gains do not affect the spatial image stability at the decoder side. To avoid this, in the simplest case (so-called simplified mode), a single gain can be assigned to all of the L channels. This can be done by analyzing all spatial signals W or a zero-order HOA coefficient sample block

It can be done by analyzing , and conversion to the spatial domain is not necessary (Fig. 4a)). The latter is equivalent to analyzing the downmix signal of W. Further details are given below.

으로부터(임의로 AO들로부터의 사이드 체이닝에 의해) 어떻게 도출될 수 있는지를 나타낸다. 0차 HOA 성분

은 DRC 분석 블록(41s)에서 분석되고, 단일의 이득 g₁이 도출된다. 단일의 이득 g₁이 DRC 이득 인코더(42s)에서 별도로 인코딩된다. 인코딩된 이득은 이어서 인코더(43)에서 HOA 신호 B와 함께 인코딩되고, 인코더(43)는 인코딩된 비트스트림을 출력한다. 임의로, 추가의 신호들(44)이 인코딩에 포함될 수 있다. 도 4의 b)는 2 개 이상의 DRC 이득들이 어떻게 HOA 표현을 공간 영역으로 변환(40)하는 것에 의해 생성되는지를 나타낸다. 변환된 HOA 신호 W _L은 이어서 DRC 분석 블록(41)에서 분석되고 이득 값들 g가 추출되어 DRC 이득 인코더(42)에서 인코딩된다. 또한 여기서, 인코딩된 이득이 인코더(43)에서 HOA 신호 B와 함께 인코딩되고, 임의로 추가 신호들(44)이 인코딩에 포함될 수 있다. 일 예로서, 후방으로부터의 소리(예컨대, 배경음(background sound))는 전방 및 측면 방향으로부터 나오는 소리보다 더 많은 감쇠를 받을 수 있다. 이것은 이 예에 대해 g 내의 (N + 1)² 개의 이득 값들이 2 개의 이득 그룹 내에서 전송될 수 있게 할 것이다. 임의로, 또한 여기서 오디오 객체 파형 및 그의 방향 정보에 의한 사이드 체이닝을 사용하는 것이 가능하다. 사이드 체이닝은 신호에 대한 DRC 이득들이 다른 신호로부터 획득된다는 것을 의미한다. 이것은 HOA 신호의 전력을 감소시킨다. 동일한 공간 소스 영역을 AO 전경음(foreground sound)과 공유하는 HOA 믹스(mix) 내의 산만하게 하는 소리(distracting sound)는 공간적으로 떨어져 있는 소리보다 더 큰 감쇠 이득을 받을 수 있다.In Figure 4, generating DRC gains for HOA is shown. 4a) shows that a single gain g ₁ (for a single gain group) is the 0th-order HOA component

(optionally by side-chaining from AOs). 0th order HOA component

is analyzed in the DRC analysis block 41s, and a unity gain g ₁ is derived. A single gain g ₁ is separately encoded in the DRC gain encoder 42s. The encoded gain is then encoded along with the HOA signal B in encoder 43, and encoder 43 outputs an encoded bitstream. Optionally, additional signals 44 may be included in the encoding. Figure 4b) shows how two or more DRC gains are created by transforming 40 the HOA representation to the spatial domain. The transformed HOA signal W _L is then analyzed in the DRC analysis block 41 and gain values g are extracted and encoded in the DRC gain encoder 42. Also here, the encoded gain is encoded together with the HOA signal B in the encoder 43, optionally further signals 44 may be included in the encoding. As an example, sound from the rear (eg, background sound) may experience more attenuation than sound from forward and side directions. This would allow the (N+1) ² gain values in g for this example to be transmitted within the 2 gain groups. Optionally, it is also possible here to use side chaining by the audio object waveform and its direction information. Side chaining means that the DRC gains for a signal are obtained from another signal. This reduces the power of the HOA signal. Distracting sounds in the HOA mix that share the same spatial source area with the AO foreground sounds may receive a greater attenuation gain than sounds that are spatially distant.

Gain values are transmitted either to the receiver side or to the decoder side.

와 그들의 개수가 전송된다. 채널 그룹들의 용도가 시그널링되고, 따라서 수신기 또는 디코더는 이득 값들을 올바르게 적용할 수 있다.A variable number of (1 to L _L = (N + 1) ² ) gain values associated with a block of τ samples are transmitted. Gain values may be assigned to channel groups for transmission. In one embodiment, all of the same gains are combined into one channel group to minimize transmitted data. When a single gain is transmitted, that gain is associated with all of the L _L channels. Channel Group Gain Values

and their number is transmitted. The usage of the channel groups is signaled so that the receiver or decoder can apply the gain values correctly.

The gain values are applied as follows.

The receiver/decoder may determine the number of coded gain values being transmitted, decode 51 related information, and assign gains to L _L = (N + 1) ² channels (52-55). If only one gain value (one channel group) is transmitted, as shown in a) of FIG. 5, the gain value may be directly applied (52) to the HOA signal ( B _DRC =g ₁ B ). . This is advantageous because decoding is much simpler and requires significantly less processing. The reason is that no matrix operations are required; This is because instead the gain values can be directly applied 52 - eg multiplied with HOA coefficients. For further details, see below.

If more than two gains are transmitted, the channel group gains are each assigned to L channel gains g = [g ₁ , ..., g _L ].

For a regular imaginary speaker grid, speaker signals with DRC gains applied are calculated by the following equation.

The resulting modified HOA expression is then calculated by the equation below.

As shown in Fig. 5b), this can be simplified. Instead of transforming the HOA signal to the spatial domain, applying gains and transforming the result back to the HOA domain, the gain vector is transformed (53) to the HOA domain by the equation:

이다. 이득 행렬이 이득 할당 블록(54)에서 HOA 계수들에 직접 적용된다: B _DRC = GB.here

to be. A gain matrix is applied directly to the HOA coefficients in the gain allocation block 54: B _DRC = GB .

This is more efficient in terms of computational work required for (N + 1) ² < τ. That is, this solution has advantages over conventional solutions because decoding is much simpler and requires significantly less processing. The reason is that no matrix operations are required; Instead, the gain values can be directly applied - eg, multiplied with the HOA coefficients in the gain allocation block 54 -.

에 의해 조작하고 DRC를 적용하며 HOA 신호를 렌더링하는 것이다:

. 이것이 도 5의 c)에 도시되어 있다. 이것은 L < τ인 경우에 유익하다.In one embodiment, a much more efficient way of applying the gain matrix is to modify the renderer matrix in the renderer matrix modification block 57 in one step.

to manipulate, apply DRC, and render the HOA signal:

. This is shown in Figure 5c). This is beneficial when L < τ.

In summary, FIG. 5 illustrates various embodiments of applying DRC to HOA signals. In Figure 5a), a single channel group gain is transmitted, decoded (51) and applied (52) directly to the HOA coefficients. The HOA coefficients are then rendered 56 using the normal rendering matrix.

In Figure 5b), more than one channel group gains are transmitted and decoded (51). As a result of decoding, a gain vector g of (N + 1) ² gain values is obtained. A gain matrix G is generated and applied (54) to the block of HOA samples. These are then rendered 56 using the normal rendering matrix.

In c) of Fig. 5, instead of directly applying the decoded gain matrix/gain values to the HOA signal, it is applied directly to the renderer's matrix. This is done in the renderer matrix modification block 57, which is computationally advantageous if the DRC block size τ is greater than the number L of output channels. In this case, the HOA samples are rendered 57 using a normal rendering matrix.

In the following, calculation of an ideal DSHT (Discrete Spherical Harmonics Transform) matrix for DRC is described. This DSHT matrix is specifically optimized for use in DRC and is different from DSHT matrices used for other purposes, such as data rate compression.

The requirements for the ideal rendering and encoding matrices D _L and D _L ^-1 related to the ideal spherical layout are derived below. Finally, these requirements are:

(1) the rendering matrix D _L must be invertible - that is, D _L ^-1 must exist;

(2) the sum of amplitudes in the spatial domain must be reflected as zero-order HOA coefficients after spatial-HOA domain transformation, and must be preserved after subsequent transformation to the spatial domain (amplitude requirement); And

(3) The energy of the spatial signal must be conserved when converting to the HOA domain and back to the spatial domain (requirement for conservation of energy).

Even for an ideal rendering layout, requirement 2 and requirement 3 seem to contradict each other. When using a simple approach to derive the DSHT transformation matrix, such as is known from the prior art, only one or the other of requirements 2 and 3 can be met without errors. As a result of meeting the requirements of either Requirement 2 or Requirement 3 without error, the error exceeds 3 dB for the other requirement. This usually causes audible artifacts. A method to overcome this problem is described below.

에 의해 주어지고, 관련된 모드 행렬이

으로서 표시된다. 각각의

은 방향

의 구면 조화함수들을 포함하는 모드 벡터(mode vector)이다. 구면 레이아웃 위치들에 관련된 L 개의 구적법 이득(quadrature gain)들은 벡터

에 모여 있다. 이 구적법 이득들은 이러한 위치들 주위의 구면 면적을 평가하고, 모두 합산하면 1의 반경을 갖는 구의 표면에 관련된 4π의 값으로 된다.First, an ideal spherical layout with L = (N + 1) ² is selected. L directions of (virtual) speaker locations

is given by, and the associated mode matrix is

is displayed as Each

silver direction

is a mode vector containing spherical harmonics of The L quadrature gains relative to the spherical layout positions are vector

are gathered in These quadrature gains evaluate the spherical area around these locations and add up to a value of 4π relative to the surface of a sphere with a radius of 1.

는 하기의 식에 의해 도출된다.First prototype rendering matrix

is derived by the following formula.

Note that division by L may be omitted due to a later normalization step (see below).

및 제2 프로토타입 행렬이 하기의 식에 의해 도출된다.Second, a compact singular value decomposition is performed:

And the second prototype matrix is derived by the following equation.

Third, the prototype matrix is normalized and:

where k represents the matrix norm type. Both matrix norm types show equally good performance. Either the k = 1 norm or the Frobenius norm must be used. This matrix satisfies requirement 3 (conservation of energy).

Fourth, in the last step, the amplitude error is substituted to satisfy requirement 2:

에 의해 계산되고, 여기서 [1,0,0,...,0]은 1의 값을 갖는 첫 번째 요소를 제외하고는 (N + 1)² 개의 모두 영인 요소들의 행 벡터이다.

은

의 행 벡터들의 합을 나타낸다. 렌더링 행렬 D _L이 이제 진폭 오차를 치환하는 것에 의해 도출되고:If the row vector e is

where [1,0,0,...,0] is a row vector of (N + 1) ^two all zero elements except for the first element which has a value of 1.

silver

represents the sum of the row vectors of The rendering matrix D _L is now derived by permuting the amplitude error:

의 모든 행에 가산된다. 이 행렬은 요구사항 2 및 요구사항 3을 충족시킨다. D _L ^-1 의 첫 번째 행 요소들은 모두 1로 된다.where vector e is

is added to all rows of This matrix satisfies requirements 2 and 3. All elements of the first row of D _L ^-1 are set to 1.

In the following, detailed requirements for DRC are described.

First, applying L _L equal gains of value g ₁ in the spatial domain is equivalent to applying gain g ₁ to the HOA coefficients:

This leads to the requirement D _L ^-1 D _L = I - meaning that L = (N + 1) ² and D _L ^-1 must exist (trivial).

Second, analyzing the sum signal in the spatial domain is equivalent to analyzing the zero-order HOA component. A DRC analyzer uses the signal's energy as well as its amplitude. As such, the sum signal is related in amplitude and energy.

은 S 개의 방향 신호들의 행렬이고;

은 방향들

에 관련된 N3D 모드 행렬이다. 모드 벡터

는 구면 조화함수로부터 구성된다. N3D 표기법에서, 0차 성분

은 방향과 무관하다.Signal model of HOA

is a matrix of S direction signals;

silver directions

is the N3D mode matrix related to mode vector

is constructed from the spherical harmonic function. In N3D notation, the zeroth order component

is independent of direction.

로 될 필요가 있다. 1 _S는 1의 값을 갖는 S 개의 요소들로 구성된 벡터이다.The zero-order component HOA signal is the sum of the direction signals to reflect the exact amplitude of the summation signal.

need to be 1 _S is a vector consisting of S elements with a value of 1.

이기 때문이다. 신호들 X _S가 상관되지 않으면 이것은

로 간단화될 것이다.The energy of the directional signals in this mix is conserved, because

because it wins If the signals X _S are uncorrelated then this

will be simplified to

에 의해 주어지고, 여기서 HOA 패닝 행렬(HOA panning matrix)

이다.The sum of the amplitudes in the spatial domain is

is given by, where the HOA panning matrix

to be.

에 대해

로 된다. 후자의 요구사항이 VBAP와 같은 패닝에서 때때로 사용되는 진폭들의 합 요구사항과 비교될 수 있다. 경험적으로, 이것이 매우 대칭적인 구면 스피커 설정에 대한 양호한 근사에서

에 의해 달성될 수 있다는 것을 알 수 있는데, 그 이유는 거기서

이기 때문이다. 진폭 요구사항이 이어서 필요한 정확도 내에 도달할 수 있다.this is

About

becomes The latter requirement can be compared to the sum of amplitudes requirement sometimes used in panning such as VBAP. Empirically, this is a good approximation for a very symmetrical spherical speaker setup.

It can be seen that it can be achieved by

because it wins Amplitude requirements can then be reached within the required accuracy.

This also ensures that the energy requirements for the sum signal can be met:

- 이상적인 대칭적 스피커 설정의 존재가 요구됨 - 로 될

에 의해 주어진다.The sum of energies in the spatial domain is, in a good approximation,

- Requires the existence of an ideal symmetrical speaker setup - to be

given by

으로 되고, 그에 부가하여, 신호 모델로부터, 재인코딩된 0차 신호가 진폭 및 에너지를 유지하기 위해 D _L ^-1의 상단 행이 [1,1,1,1,..] - 즉, "1" 요소들을 갖는 길이 L의 벡터 - 일 필요가 있는 것으로 결론내릴 수 있다. this is a requirement

, and in addition, from the signal model, the top row of D _L ^-1 is [1,1,1,1,..] - that is, "1 It can be concluded that it needs to be " a vector of length L with elements.

의 에너지가 HOA로의 변환 및 스피커에 대한 공간 렌더링 후에 신호의 방향

에 관계없이 보존되어야만 한다. 이것은

로 된다. 이것은 D _L을 회전 행렬 및 대각 이득 행렬

로부터 모델링하는 것에 의해 달성될 수 있다(방향

에의 의존성이 명확성을 위해 제거되었음):

Third, conservation of energy is a prerequisite: signal

The direction of the signal after the energy of the conversion to HOA and spatial rendering to the speaker

Regardless, it must be preserved. this is

becomes This converts D _L into a rotation matrix and a diagonal gain matrix

can be achieved by modeling from

dependence has been removed for clarity):

에 대해, 따라서

에 관련된 모든 이득들 a_o ²이 방정식을 충족시킬 것이다. 모든 이득들이 똑같게 선택되면, 이것은 a_o ² = (N + 1)^-2으로 된다.spherical harmonic function

about, therefore

All gains related to a _o ² will satisfy this equation. If all gains are chosen equally, this becomes a _o ² = (N + 1) ^-2 .

The requirement VV ^T = 1 can be achieved for L ≥ (N + 1) ² and can only be approximated for L < (N + 1) ² .

(단,

임)으로 된다.this is a requirement

(only,

im) becomes

As an example, the case with ideal spherical positions (for HOA orders N=1 to N=3) is described below (Tables 1 to 3). The ideal spherical positions for additional HOA orders (N=4 to N=6) are further described below (Tables 4-6). All of the locations mentioned below are derived from the modified locations published in [1]. A method for deriving these positions and the related quadrature gains/cubature gains was presented in [2]. In these tables, the azimuth angle is measured counterclockwise from the front direction relative to the listening position, and the inclination angle is measured from the z-axis, with an inclination angle of zero being above the listening position.

N=1 positions

a)

b)

Table 1: a) Spherical positions of imaginary speakers for HOA order N=1, and b) Rendering matrix for the resulting spatial transform (DSHT)

N=2 positions

a)

b)

Table 2: a) Spherical positions of imaginary speakers for HOA order N=2, and b) Rendering matrix for the resulting spatial transform (DSHT)

N=3 positions

Table 3 a): Spherical positions of imaginary speakers for HOA order N=3

b)

Table 3 b): Rendering matrix for the resulting spatial transformation (DSHT)

The term numerical quadrature is often shortened to quadrature, and is in fact a synonym for numerical integration, especially when applied to one-dimensional integrals. Numerical integration over more than one dimension is referred to herein as a cubature.

As described above, a typical application scenario of applying a DRC gain to an HOA signal is shown in FIG. 5 . For mixed content applications, eg HOA + audio objects, DRC gain application can be realized in at least two ways for flexible rendering.

6 shows DRC (Dynamic Range Compression) processing on the decoder side as an example. In Fig. 6a), DRC is applied before rendering and mixing. In Fig. 6 b), DRC is applied to the speaker signal - ie after rendering and mixing.

를 분석하여 도출될 수 있으며 여기서 y _m은 0차 HOA 신호 b _w와 S 개의 오디오 객체들 x _S의 모노 다운믹스(mono downmix)의 믹스이다:In Fig. 6 a), DRC gains are applied to audio objects and HOA separately: DRC gains are applied to audio objects in audio object DRC block 610, DRC gains are applied to HOA in DRC block 615, HOA applies to The realization of the HOA DRC block 615 here is consistent with one of those in FIG. 5 . In b) of FIG. 6, a single gain is applied to all channels of the mixed signal of the rendered HOA and the rendered audio object signal. Spatial emphasis and attenuation are not possible here. A related DRC gain cannot be created by analyzing the sum signal of the rendered mix, since the speaker layout at the consumer site is not known at the time of creation at the broadcast or content creation site. DRC gain

where y _m is the mix of the zero-order HOA signal b _w and the mono downmix of the S audio objects x _S :

In the following, further details of the disclosed solution are described.

DRC for HOA content

DRC may be applied to the HOA signal prior to rendering, or may be combined with rendering. DRC for HOA can be applied in the time domain or in the QMF filter bank domain.

를 제공한다.For DRC in the time domain, the DRC decoder selects (N + 1) ^two gain values according to the number of HOA coefficient channels of HOA signal c .

provides

N is the HOA order.

DRC gains are applied to the HOA signals according to the equation:

의 일회성 샘플의 벡터이고,

및 그의 역 D _L ^-1은 DRC를 위해 최적화된 DSHT(Discrete Spherical Harmonics Transform)에 관련된 행렬이다.where c is the HOA coefficients

is a vector of one-time samples of

and its inverse D _L ^-1 is a matrix related to a Discrete Spherical Harmonics Transform (DSHT) optimized for DRC.

에 의해 직접 계산하는 것이 샘플당 (N + 1)⁴ 개의 연산들에 의해 계산 부하를 감소시키는 데 유리할 수 있고, 여기서 D는 렌더링 행렬이고 (D D _L ^-1)은 미리 계산될 수 있다.In one embodiment, a rendering step is included and the speaker signals are

It may be advantageous to reduce the computational load by (N + 1) ⁴ operations per sample, where D is the rendering matrix and ( D D _L ^-1 ) may be precomputed.

이, 단순화된 모드에서와 같이, g _drc 의 동일한 값을 가지는 경우, 단일의 이득 그룹이 코더 DRC 이득들을 전송하는 데 사용되었다. 이 경우는 DRC 디코더에 의해 플래깅될 수 있는데, 그 이유는 이 경우에 공간 필터에서의 계산이 필요하지 않고, 따라서 계산이 하기의 식으로 단순화되기 때문이다:all the benefits

With the same value of g _drc , as in the simplified mode, a single gain group was used to transmit the coder DRC gains. This case can be flagged by the DRC decoder, since in this case no calculation in the spatial filter is needed, and thus the calculation is simplified to the equation:

The above describes how to obtain and apply DRC gain values. In the following, the calculation of DSHT matrices for DRC is described.

을 결정하는 행렬은 다음과 같이 계산된다:In the following, D _L is renamed to D _DSHT . Spatial filter D _DSHT and its inverse

The matrix that determines is computed as:

(단,

임) 및 관련된 구적법(입체 구적법) 이득들

의 세트가 선택된다. 이 위치들에 관련된 모드 행렬

가 앞서 기술된 바와 같이 계산된다. 즉, 모드 행렬

는

에 따른 모드 벡터들을 포함하고, 각각의

은 미리 정의된 방향

(단,

임)의 구면 조화함수를 포함하는 모드 벡터이다. 미리 정의된 방향은, (예로서 1≤N≤6에 대한) 표 1 내지 표 6에 따라, HOA 차수 N에 의존한다. 제1 프로토타입 행렬이

에 의해 계산된다(후속하는 정규화로 인해 (N+1)²으로 나누는 것이 생략될 수 있다). 콤팩트한 특이값 분해가 수행되고

, 새로운 프로토타입 행렬이

에 의해 계산된다. 이 행렬은

에 의해 정규화된다. 행 벡터 e가

에 의해 계산되고, 여기서 [1,0,0,...,0]은 1의 값을 갖는 첫 번째 요소를 제외하고는 (N + 1)² 개의 모두 영인 요소들의 행 벡터이다.

는

의 행들의 합을 나타낸다. 최적화된 DSHT 행렬 D _DSHT가 이제

에 의해 도출된다. -e가 e 대신에 사용되는 경우, 본 발명이 약간 더 나쁘지만 여전히 사용가능한 결과들을 제공한다는 것을 알았다.Spherical positions, indexed by HOA order N from Tables 1-4

(only,

) and related quadrature (solid quadrature) gains

A set of is selected. The mode matrix associated with these positions

is calculated as described above. That is, the mode matrix

Is

It includes mode vectors according to , and each

is a predefined direction

(only,

is the mode vector including the spherical harmonic function of (i). The predefined direction depends on the HOA order N, according to Tables 1 to 6 (eg for 1≤N≤6). The first prototype matrix is

(Dividing by (N+1) ² may be omitted due to subsequent regularization). A compact singular value decomposition is performed and

, the new prototype matrix is

is calculated by this matrix

normalized by If the row vector e is

where [1,0,0,...,0] is a row vector of (N + 1) ^two all zero elements except for the first element which has a value of 1.

Is

represents the sum of the rows of The optimized DSHT matrix D _DSHT is now

is derived by - found that when e is used instead of e , the present invention gives slightly worse but still usable results.

For DRC in the QMF filter bank domain, the following applies.

에 배열되어 있다.The DRC decoder provides a gain value g _ch (n, m) for every temporal frequency tile n, m for (N + 1) ^two spatial channels. The gains for time slot n and frequency band m are

are arranged in

는 τ 개의 HOA 샘플들의 블록이며,

는 QMF 필터 뱅크의 입력 시간 세분성(input time granularity)과 일치하는 공간 샘플들의 블록이다. 이어서, QMF 분석 필터 뱅크가 적용된다.

이 시간 주파수 타일 (n, m)마다의 공간 채널들의 벡터를 나타낸다고 하자. 이어서, DRC 이득들이 적용된다:

.Multiband DRC (multiband DRC) is applied in the QMF filter bank area. Processing steps are shown in FIG. 7 . The reconstructed HOA signals are transformed to the spatial domain by (inverse DSHT): W _DSHT = D _DSHT C , where

is a block of τ HOA samples,

is a block of spatial samples matching the input time granularity of the QMF filter bank. The QMF analysis filter bank is then applied.

Let us denote a vector of spatial channels per this time-frequency tile (n, m). DRC gains are then applied:

.

, 여기서 D는 HOA 렌더링 행렬을 나타낸다. QMF 신호들은 이어서 추가 처리를 위해 믹서에 피드될 수 있다.To minimize computational complexity, DSHT and rendering for speaker channels are combined:

, where D represents the HOA rendering matrix. The QMF signals can then be fed to a mixer for further processing.

Figure 7 shows the DRC for HOA in the QMF domain combined with the rendering step.

If only a single gain group for DRC is used, this should be flagged by the DRC decoder, again because it allows computational simplification. In this case, all of the gains in the vector g (n, m) share the same value of g _DRC (n, m). The QMF filter bank can be applied directly to the HOA signal, and the gain g _DRC (n, m) can be multiplied in the filter bank domain.

Figure 8 shows the DRC for the HOA in the QMF domain (the filter domain of a Quadrature Mirror Filter (QMF)) combined with a rendering step, with computational simplifications for the simple case of a single DRC gain group.

As will be apparent from consideration of the foregoing, in one embodiment, the present invention relates to a method of applying dynamic range compression gain factors to an HOA signal, the method comprising: receiving an HOA signal and one or more gain factors; Transforming the signal to the spatial domain (40) - iDSHT is used with a transform matrix and quadrature gains (q) obtained from the spherical positions of the imaginary speakers, and a transformed HOA signal is obtained - transforming the gain factors into Multiplying with the HOA signal - obtaining a dynamic range compressed transformed HOA signal - and converting the dynamic range compressed transformed HOA signal back to the HOA domain as a coefficient domain using DSHT (Discrete Spherical Harmonics Transform) - A dynamic range compressed HOA signal is obtained.

에 따라 계산되고, 여기서

은

의 정규화된 버전이고, U,V는

으로부터 획득되며,

는 가상 스피커들의 사용된 구면 위치들에 관련된 구면 조화함수의 전치 모드 행렬(transposed mode matrix)이고, e ^T는

의 전치된 버전(transposed version)이다.Moreover, the transformation matrix is

is calculated according to, where

silver

is the normalized version of, and U, V are

is obtained from

is the transposed mode matrix of the spherical harmonic function relative to the used spherical positions of the imaginary speakers, and e ^T is

is a transposed version of

에 따라 계산되고, 여기서

은

의 정규화된 버전이고, U,V는

으로부터 획득되며,

는 가상 스피커들의 사용된 구면 위치들에 관련된 구면 조화함수의 전치 모드 행렬이고, e ^T는

의 전치된 버전이다.Moreover, in one embodiment, the present invention relates to a device for applying DRC gain factors to an HOA signal, the device receiving the HOA signal and one or more gain factors, transforming the HOA signal to the spatial domain (40 ) - iDSHT is used with the transform matrix and quadrature gains (q) obtained from the spherical positions of the imaginary speakers, and a transformed HOA signal is obtained - multiplying the gain factors with the transformed HOA signal - dynamic range compressed A transformed HOA signal is obtained - and converting the dynamic range compressed transformed HOA signal back to the HOA domain, which is a coefficient domain, using DSHT (Discrete Spherical Harmonics Transform) - a dynamic range compressed HOA signal is obtained - A processor or one or more processing elements configured for Moreover, the transformation matrix is

is calculated according to, where

silver

is the normalized version of, and U, V are

is obtained from

is the transposition mode matrix of the spherical harmonic function relative to the used spherical positions of the imaginary speakers, and e ^T is

is a transposed version of

에 따라 계산되고, 여기서

은

의 정규화된 버전이고, U,V는

으로부터 획득되며,

는 가상 스피커들의 사용된 구면 위치들에 관련된 구면 조화함수의 전치 모드 행렬이고, e ^T는

의 전치된 버전이다.Moreover, in one embodiment, the invention provides a computer readable storage having computer executable instructions that, when executed on a computer, cause the computer to perform a method of applying dynamic range compression gain factors to a Higher Order Ambisonics (HOA) signal. medium, the method comprises receiving an HOA signal and one or more gain factors, transforming the HOA signal to the spatial domain (40) - transform matrix obtained by iDSHT from spherical positions of imaginary speakers and quadrature gains used with (q), a transformed HOA signal is obtained - multiplying the gain factors with the transformed HOA signal - a dynamic range compressed transformed HOA signal is obtained - and a dynamic range compressed transformed HOA signal A step of converting back to the HOA domain, which is the coefficient domain, using Discrete Spherical Harmonics Transform (DSHT) - a dynamic range compressed HOA signal is obtained. Moreover, the transformation matrix is

is calculated according to, where

silver

is the normalized version of, and U, V are

is obtained from

is the transposition mode matrix of the spherical harmonic function relative to the used spherical positions of the imaginary speakers, and e ^T is

is a transposed version of

Moreover, in one embodiment, the present invention relates to a method of performing DRC on an HOA signal, the method comprising steps of setting or determining a mode, wherein the mode is either a simplified mode or a non-simplified mode, In the simplified mode, transforming the HOA signal to the spatial domain - inverse DSHT is used -, in the unsimplified mode, analyzing the transformed HOA signal, in the simplified mode, analyzing the HOA signal, the analyzing obtaining, from the results of step, one or more gain factors usable for dynamic range compression, in simplified mode only one gain factor is obtained and in non-simplified mode two or more different gain factors are obtained; In the simplified mode, the obtained gain factors are multiplied with the HOA signal - a gain-compressed HOA signal is obtained -, in the non-simplified mode, the obtained gain factors are multiplied with the transformed HOA signal - the gain-compressed converted HOA signal is obtained - and converting the gain-compressed transformed HOA signal back to the HOA domain - the gain-compressed HOA signal is obtained.

In one embodiment, the method includes receiving an indication indicating either a simplified mode or an unsimplified mode, selecting a non-simplified mode if the indication indicates an unsimplified mode, and If a simplified mode is indicated, further comprising selecting the simplified mode, wherein converting the HOA signal to the spatial domain and converting the dynamic range compressed transformed HOA signal back to the HOA domain mode only, where in the simplified mode, only one gain factor is multiplied with the HOA signal.

In one embodiment, the method comprises analyzing the HOA signal in a simplified mode and analyzing the transformed HOA signal in an unsimplified mode, and then, from the results of the analyzing step, one usable for dynamic range compression. obtaining the above gain factors, wherein in the unsimplified mode at least two different gain factors are obtained and in the simplified mode only one gain factor is obtained, wherein in the simplified mode the gain compressed HOA A signal is obtained by the step of multiplying the obtained gain factor with the HOA signal, wherein in the non-simplified mode, the gain-compressed transformed HOA signal is obtained by multiplying two or more obtained gain factors with the transformed HOA signal. is obtained, where in the unsimplified mode, the above step of converting the HOA signal to the spatial domain uses inverse DSHT.

In one embodiment, the HOA signal is divided into frequency subbands, and the gain factor(s) are obtained and applied individually to each frequency subband, using individual gains per subband. In one embodiment, analyzing the HOA signal (or transformed HOA signal), obtaining one or more gain factors, multiplying the obtained gain factor(s) by the HOA signal (or transformed HOA signal), and The step of converting the gain compressed transformed HOA signal back to the HOA domain is applied separately to each frequency subband, using individual gains for each subband. Note that the sequential order of dividing the HOA signal into frequency subbands and transforming the HOA signal to the spatial domain can be reversed, and/or synthesizing the subbands and converting the gain-compressed transformed HOA signals back to the HOA The sequential order of transforming into regions can change and is independent of each other.

In one embodiment, the method further comprises, prior to the step of multiplying the gain factors, transmitting the converted HOA signal along with the obtained gain factors and the number of the gain factors.

및 대응하는 구적법 이득들로부터 계산되고, 여기서 모드 행렬

는

에 따른 모드 벡터들을 포함하고, 각각의

은 미리 정의된 방향

(단,

임)의 구면 조화함수를 포함하는 모드 벡터이다. 미리 정의된 방향은 HOA 차수 N에 의존한다.In one embodiment, the transformation matrix is the mode matrix

and the corresponding quadrature gains, where the mode matrix

Is

It includes mode vectors according to , and each

is a predefined direction

(only,

is the mode vector including the spherical harmonic function of (i). The predefined direction depends on the HOA order N.

에 따라 상이한 제2 공간 영역으로 변환하는 추가 단계를 포함하고, 여기서

는 초기화 페이즈에서

에 따라 미리 계산되며, 여기서 D는 HOA 신호를 상이한 제2 공간 영역으로 변환하는 렌더링 행렬이다.In one embodiment, the HOA signal B is transformed to the spatial domain to obtain the transformed HOA signal W _DSHT , the transformed HOA signal W _DSHT is the gain values diag in units of samples according to W _DSHT = diag( g ) D _L B ( g ), and this method converts the converted HOA signal

and an additional step of converting to a second spatial domain different according to , where

in the initialization phase

It is calculated in advance according to , where D is a rendering matrix for transforming the HOA signal into a different second spatial domain.

In one embodiment, if at least (N + 1) ² < τ (where N is the HOA degree and τ is the DRC block size), the method calculates G = D _L ^-1 diag ( g ) D _L (where N is the HOA degree and τ is the DRC block size). where G is the gain matrix and DL is the DSHT matrix defining the DSHT), converting the gain vector to the HOA domain (53), and converting the gain matrix G to the HOA coefficients of the HOA signal B according to B _DRC = GB and further comprising a step of applying - DRC compressed HOA signal B _DRC is obtained.

에 따라 이득 행렬 G를 렌더러 행렬 D에 적용하는 단계 - 동적 범위 압축된 렌더러 행렬

가 획득됨 -, 및 동적 범위 압축된 렌더러 행렬을 사용해 HOA 신호를 렌더링하는 단계를 추가로 포함한다.In one embodiment, if at least L < τ, where L is the number of output channels and τ is the DRC block size, the method

Applying the gain matrix G to the renderer matrix D according to - dynamic range compressed renderer matrix

is obtained - and rendering the HOA signal using the dynamic range compressed renderer matrix.

In one embodiment, the present invention relates to a method of applying DRC gain factors to an HOA signal, the method comprising receiving the HOA signal with an indication and one or more gain factors, the indication being in a simplified mode or an unsimplified mode. Indicates either of the modes, and only one gain factor is received if the indication indicates the simplified mode - selecting either the simplified or non-simplified mode according to the indication, in the simplified mode: Multiplying the gain factor with the HOA signal - a dynamic range compressed transformed HOA signal is obtained - in non-simplified mode, transforming the HOA signal to the spatial domain - a transformed HOA signal is obtained - transforming the gain factors multiplying with the HOA signals, dynamic range compressed transformed HOA signals are obtained, and converting the dynamic range compressed transformed HOA signals back to the HOA domain, dynamic range compressed HOA signals are obtained. include

Moreover, in one embodiment, the present invention relates to a device that performs DRC on an HOA signal, wherein the device sets or determines a mode, wherein the mode is either a simplified mode or a non-simplified mode, In the simplified mode, the HOA signal is transformed into the spatial domain - inverse DSHT is used - and the unsimplified mode analyzes the transformed HOA signal, whereas in the simplified mode, the HOA signal is analyzed. From the results, obtaining one or more gain factors usable for dynamic range compression, in simplified mode only one gain factor is obtained and in non-simplified mode two or more different gain factors are obtained; In mode, the acquired gain factors are multiplied by the HOA signal - a gain compressed HOA signal is obtained - in the non-simplified mode, the obtained gain factors are multiplied by the transformed HOA signal - a gain compressed transformed HOA signal is obtained - a processor or one or more processing elements configured for, and converting the gain-compressed transformed HOA signal back to the HOA domain, wherein the gain-compressed HOA signal is obtained.

In one embodiment for the non-simplified mode only, the device performing DRC on the HOA signal transforms the HOA signal to the spatial domain, analyzes the transformed HOA signal, and from the results of the analysis, the dynamic range Obtaining gain factors usable for compression, multiplying the obtained factors by transformed HOA signals, obtaining gain-compressed transformed HOA signals, and obtaining the gain-compressed transformed HOA signals back into the HOA domain. and a processor or one or more processing elements configured for converting - gain compressed HOA signals are obtained. In one embodiment, the device further includes a transmission unit that transmits the HOA signal together with the obtained gain factor or gain factors before multiplying the obtained gain factor or gain factors.

It should also be noted here that the sequential order of dividing the HOA signal into frequency subbands and transforming the HOA signal into the spatial domain can be changed, synthesizing the subbands and transforming the gain-compressed HOA signals back into the HOA domain. The sequential order of converting to can change and is independent of each other.

Moreover, in one embodiment, the present invention relates to a device that applies DRC gain factors to an HOA signal, the device receiving the HOA signal with an indication and one or more gain factors - the indication being in a simplified mode or non-simplified mode. Indicates any of the simplified modes, and only one gain factor is received if the indication indicates the simplified mode - depending on the indication, setting the device to either the simplified or non-simplified mode, simplification in the reduced mode, the gain factor is multiplied with the HOA signal - a dynamic range compressed transformed HOA signal is obtained; In the non-simplified mode, transforming the HOA signal to the spatial domain, a transformed HOA signal is obtained, multiplying gain factors with the transformed HOA signals, dynamic range compressed transformed HOA signals are obtained, and a processor or one or more processing elements configured for converting the dynamic range compressed transformed HOA signals back to the HOA domain, wherein the dynamic range compressed HOA signal is obtained.

In one embodiment, the device further includes a transmitting unit that transmits the HOA signal together with the obtained gain factors before multiplying by the obtained factors. In one embodiment, the HOA signal is divided into frequency subbands, analyzing the transformed HOA signal, obtaining gain factors, multiplying the obtained factors by the transformed HOA signals, and gain compressed transformed HOA signal. Transformation of the HOA signals back to the HOA domain is applied separately to each frequency subband, with individual gains per subband.

In one embodiment of a device for applying DRC gain factors to an HOA signal, the HOA signal is divided into a plurality of frequency subbands, obtaining one or more gain factors, and combining the obtained gain factors into the HOA signal or a transformed HOA signal. Multiplying with , and converting the gain-compressed transformed HOA signals back to the HOA domain in the non-simplified mode are applied individually to each frequency subband, using individual gains for each subband.

Moreover, in one embodiment in which only the non-simplified mode is used, the present invention relates to a device that applies DRC gain factors to an HOA signal, the device receiving the HOA signal together with the gain factors, (iDSHT transforming the HOA signal to the spatial domain, a transformed HOA signal is obtained, multiplying gain factors with the transformed HOA signal, a dynamic range compressed transformed HOA signal is obtained, and dynamic range compression. A processor or one or more processing elements configured for converting (using DSHT) the converted HOA signal back to the HOA domain (ie coefficient domain), wherein a dynamic range compressed HOA signal is obtained.

Tables 4 to 6 below list the spherical positions of imaginary speakers for an HOA of order N (where N = 4, 5 or 6).

While the basic novel features of the present invention as applied to the preferred embodiments of the present invention are shown, described, and referenced, in the apparatus and method described, in the form and detail of the devices disclosed, and in their operation. It will be appreciated that various omissions and substitutions and changes of can be made by those skilled in the art without departing from the spirit of the present invention. All combinations of those elements that perform substantially the same function in substantially the same way to achieve the same results are expressly intended to be within the scope of the invention. Substitution of elements from one described embodiment to another is fully intended and contemplated.

It will be appreciated that the invention has been described purely as an example and that modifications of detail may be made without departing from the scope of the invention. Each feature disclosed in the description and (where appropriate) the claims and drawings may be provided independently or in any suitable combination.

Features may be implemented in hardware, software, or a combination of the two, where appropriate.

References:

[1] "Integration nodes for the sphere", Jorg Fliege 2010, online accessed 2010-10-05 http://www.mathematik.uni-dortmund.de/lsx/research/projects/fliege/nodes/nodes.html

[2] "A two-stage approach for computing cubature formulae for the sphere", Jorg Fliege and Ulrike Maier, Technical report, Fachbereich Mathematik, Universitat Dortmund, 1999

N=4 positions

Table 4: Spherical positions of imaginary speakers for HOA order N=4

N=5 positions

Table 5: Spherical positions of imaginary speakers for HOA order N=5

N=6 positions

Table 6: Spherical positions of imaginary speakers for HOA order N=6

Claims (5)

As a method for dynamic range compression (DRC),
receiving a reconstructed Higher Order Ambisonics (HOA) audio signal representation;
Converting the reconstructed HOA audio signal to a spatial domain based on W _DSHT = D _DSHT C
- D _DSHT corresponds to the inverse DSHT (Discrete Spherical Harmonics Transform) matrix, C corresponds to a block of τ HOA samples, and W corresponds to the input time granularity of the QMF (Quadrature Mirror Filter) bank. Corresponds to a block of spatial samples -; and

Applying a DRC gain value g (n, m) corresponding to the time-frequency tile (n, m) based on
-

is the vector of spatial channels for the time-frequency tile (n, m), and the DSHT matrix is the prototype matrix

and based on row vector e -
Including, method. According to claim 1,
wherein the reconstructed HOA audio signal representation is divided into frequency subbands, and the DRC gain value is applied to each subband individually. A non-transitory computer-readable storage medium having computer-executable instructions that when executed on a computer cause the computer to perform the method of claim 1 . An apparatus for dynamic range compression (DRC),
a receiver for receiving a reconstructed Higher Order Ambisonics (HOA) audio signal representation; and
audio decoder
and the audio decoder:
Converting the reconstructed HOA audio signal to the spatial domain based on W _DSHT = D _DSHT C
- D _DSHT corresponds to the inverse DSHT (Discrete Spherical Harmonics Transform) matrix, C corresponds to a block of τ HOA samples, and W corresponds to the input time granularity of the QMF (Quadrature Mirror Filter) bank. Corresponds to a block of spatial samples -,

To apply a DRC gain value g (n, m) corresponding to the time-frequency tile (n, m) based on
-

is the vector of spatial channels for the time-frequency tile (n, m), and the DSHT matrix is the prototype matrix

and based on row vector e -,
configured device. According to claim 4,
wherein the reconstructed HOA audio signal representation is divided into frequency subbands, and the DRC gain value is applied individually to each subband.

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